U.S. patent number 5,883,646 [Application Number 08/551,297] was granted by the patent office on 1999-03-16 for compact flex-circuit for modular assembly of optical sensor components in an inkjet printer.
This patent grant is currently assigned to Hewlett-Packard Company. Invention is credited to Robert W. Beauchamp.
United States Patent |
5,883,646 |
Beauchamp |
March 16, 1999 |
Compact flex-circuit for modular assembly of optical sensor
components in an inkjet printer
Abstract
A carriage-mounted optical sensor for a color inkjet
printer/plotter includes a modular flex-circuit assembly which has
a co-planar junction which directly interconnects with all
electronic components such as through conductive support leads from
a photocell and LEDs. Additional components are then
self-attachable to the modular flex-circuit assembly to form an
optical sensor unit having the LEDs positioned to transmit light to
a print zone, and having the photocell positioned to receive
reflected light from the print zone. A cover provides a protective
shield for the electronics in the optical sensor, and is
self-attachable in a predetermined position on the carriage.
Separate activation circuits are provided for each LED to allow
different LEDs to be selectively activated depending on the type of
markings on the media.
Inventors: |
Beauchamp; Robert W. (Carlsbad,
CA) |
Assignee: |
Hewlett-Packard Company (Palo
Alto, CA)
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Family
ID: |
26734435 |
Appl.
No.: |
08/551,297 |
Filed: |
October 31, 1995 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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540908 |
Oct 11, 1995 |
5600350 |
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55624 |
Apr 30, 1993 |
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Current U.S.
Class: |
347/19;
347/37 |
Current CPC
Class: |
B41J
25/34 (20130101); B41J 29/393 (20130101); B41J
11/008 (20130101); B41J 2/2135 (20130101); B41J
11/42 (20130101); B41J 19/142 (20130101) |
Current International
Class: |
B41J
11/42 (20060101); B41J 2/21 (20060101); B41J
25/34 (20060101); B41J 25/00 (20060101); B41J
29/393 (20060101); B41J 11/00 (20060101); B41J
029/393 () |
Field of
Search: |
;347/19,37,40,43
;356/372,402,445,448 ;250/226,208.2,578.1 |
References Cited
[Referenced By]
U.S. Patent Documents
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4471384 |
September 1984 |
Sato et al. |
5170047 |
December 1992 |
Beauchamp et al. |
5353052 |
October 1994 |
Suzuki et al. |
5600350 |
February 1997 |
Cobbs et al. |
|
Primary Examiner: Metjahic; Safet
Assistant Examiner: Chizmar; John
Attorney, Agent or Firm: Romney; David S.
Parent Case Text
This application is a continuation-in-part of Ser. No. 08/540,908
filed on Oct. 11, 1995 (now U.S. Pat. No. 5,600,350), which is a
continuation of Ser. No. 55,624 filed on Apr. 30, 1993 in the names
of Keith E. Cobbs, Robert W. Beauchamp and Paul R. Sorenson.
Claims
I claim as my invention:
1. A printer/plotter with one or more inkjet printheads for
applying ink to media in a print zone, comprising:
a carriage for holding said printheads in a stationary position a
predetermined distance over said print zone while said carriage
moves in a carriage scan direction across said media;
an optical sensor unit mountable on said carriage;
at least one light source on said optical sensor unit for
transmitting light to said print zone;
a photocell on said optical sensor unit for receiving light
reflected from said print zone; and
a modular circuit assembly having a single co-planar end junction
portion to electrically interconnect and support said light source,
and to electrically interconnect and support said photocell;
and
a protective casing for holding said optical sensor unit, said
casing mounting said optical sensor unit in a fixed position on
said carriage.
2. The printer/plotter of claim 1 wherein said light source
includes an LED.
3. The printer/plotter of claim 1 wherein said light source
includes at least two light sources each emitting a different color
of light for use in alignment calibration of inkjet printheads.
4. The printer/plotter of claim 1 wherein said modular circuit
assembly includes a flex-circuit with said co-planar junction
portion located at one end of said flex-circuit.
5. The printer/plotter of claim 1 which further includes a
plurality of inkjet printheads each having a different color of
ink.
6. The printer/plotter of claim 5 wherein said plurality of inkjet
printheads includes color inks taken from the group of cyan,
yellow, magenta, black, red, green and blue.
7. The printhead/plotter of claim 1 wherein said casing is
self-attachable to said carriage through X/Y/Z position datums.
8. The printhead/plotter of claim 1 wherein said modular circuit
assembly includes a flex-circuit co-planar junction portion having
through-holes for interconnection with supportive conductive wires
from said light source and from said photocell, respectively.
9. The printhead/plotter of claim 8 wherein all of the electronic
elements of said optical sensor unit are connected to said modular
circuit assembly through said co-planar junction portion.
10. The printhead/plotter of claim 9 wherein all of said electronic
elements of said optical sensor are supported from one side of said
flex-circuit co-planar junction portion.
11. A method for modular assembly of optical sensor components for
an inkjet printer/plotter, comprising:
making a first modular component by attaching at least one light
source and a photocell to one co-planar junction portion of a
flex-circuit;
creating a second composite modular component formed by combining
the first modular component with a plurality of structural elements
for positioning the light source and the photocell relative to each
other;
providing a third modular component constituting a protective
casing; and
attaching the casing to the second composite modular component to
form an optical sensor unit.
12. The method of claim 11 wherein said creating step includes
combining the first modular component with a light tube which is
optically aligned with the light source.
13. The method of claim 11 wherein said providing step includes
providing a casing having X/Y/Z axis positioning datums, and
wherein said attaching step includes placing the X/Y/Z axis
positioning datums in engagement with matching datums on the
printer carriage.
14. The method of claim 11 wherein said making step includes
providing an electrical connection through a common junction
portion between the flex-circuit on the one hand and the light
source and photocell on the other hand.
15. The method of claim 11 wherein said making step includes
providing a support through a common junction portion between the
flex-circuit on the one hand and the light source and photocell on
the other hand.
16. The method of claim 11 wherein said making step includes
providing an electrical and supportive connection between a common
junction portion at one end of the flex-circuit on the one hand and
the light source and photocell on the other hand.
17. The method of claim 11 which further includes mounting the
optical sensor unit formed by said attaching step to a printer
carriage.
18. An optical sensor unit for an inkjet printer carriage,
comprising:
a first modular component having a flex-circuit directly attached
at a common co-planar junction portion through wire leads to at
least one light source and a photocell;
a plurality of structural elements for positioning the light source
and the photocell relative to each other; and
a second modular component having a casing for said light source
and said photocell.
19. The optical sensor unit of claim 18 which further includes
first terminal means at one end of said flex-circuit for providing
a junction with all circuit elements of said optical sensor, and
second terminal means an an opposite end of said flex-circuit for
providing an electrical connection with a circuit board on the
inkjet printer carriage.
20. The optical sensor unit of claim 18 wherein said casing
includes first self-attachment means integral with said casing for
positioning said light source and said photocell.
21. The optical sensor unit of claim 18 wherein said casing
includes second self-attachment means integral with said casing for
mounting the optical sensor unit in a predetermined position on the
inkjet printer carriage.
22. The optical sensor unit of claim 21 which further includes a
plurality of printheads mounted on the carriage for applying ink to
a print zone as the carriage moves along a scan axis.
23. The optical sensor unit of claim 22 wherein said casing is
mounted in a predetermined position on the inkjet printer carriage
to enable light transmitted from the light source to said print
zone to be reflected back toward said photocell.
24. The optical sensor unit of claim 18 wherein said second modular
component includes ESD shielding surrounding the active electronic
components of said optical sensor unit.
25. The optical sensor unit made by the steps of claim 11.
26. A printer/plotter with a plurality of inkjet printheads for
applying different color inks to media in a print zone,
comprising:
a carriage for holding said printheads in a stationary position a
predetermined distance over said print zone while said carriage
moves in a carriage scan direction across said media;
an optical sensor unit mountable on said carriage;
at least two light sources on said optical sensor unit for
transmitting light to the media, each light source emitting light
of a different color for use in alignment calibration;
a photocell on said optical sensor unit for receiving light
reflected from the media;
a circuit assembly having a junction portion to electrically
interconnect and support said light sources, and to electrically
interconnect and support said photocell; and
a separate actuation circuit for each of said at least two light
sources to selectively activate them based on the type of markings
on the media.
27. The printer/plotter of claim 26 wherein said light sources
include LEDs.
28. The printer/plotter of claim 27 wherein said light sources
include at least one LED emitting green light and at least one LED
emitting non-green light.
29. The printer/plotter of claim 28 wherein said light sources
include at least one LED emitting blue light.
30. The printer/plotter of claim 26 wherein said separate actuation
circuits selectively activate said at least two light sources only
one-at-a-time.
Description
RELATED APPLICATIONS
This application is related to the following commonly assigned
co-pending applications which are incorporated herein by reference:
Ser. No. 08/558,571 now issued as a U.S. patent entitled UNITARY
LIGHT TUBE FOR MOUNTING OPTICAL SENSOR COMPONENTS ON AN INKJET
PRINTER CARRIAGE filed Oct. 31, 1995 in the name of Robert W.
Beauchamp; and Ser. No. 08/551,022 entitled OPTICAL PATH
OPTIMIZATION FOR LIGHT TRANSMISSION AND REFLECTION IN A
CARRIAGE-MOUNTED INKJET PRINTER SENSOR filed Oct. 31, 1995 in the
names of Robert W. Beauchamp, Isidre Rosello and Josep
Tarradas.
BACKGROUND OF THE INVENTION
This invention relates generally to inkjet printers/plotters, and
more specifically to carriage-mounted optical sensors in an inkjet
printer/plotter.
Many print quality benefits are achieved by mounting an optical
sensor on a carriage which also carries printing elements, since
the optical sensor can then pass over the media upon which the
printing elements are applying alphanumeric indicia, graphics or
images. For example, see commonly assigned U.S. Pat. No. 5,170,047
entitled OPTICAL SENSOR FOR PLOTTER PEN VERIFICATION, and U.S. Pat.
No. 5,448,269 entitled MULTIPLE INKJET CARTRIDGE ALIGNMENT FOR
BIDIRECTIONAL PRINTING BY SCANNING A REFERENCE PATTERN, both of
which are incorporated herein by reference.
The full color inkjet printer/plotters which have been developed
comprise a plurality of inkjet pens of diverse colors. A typical
color inkjet printer/plotter has four inkjet pens, one that stores
black ink, and three that store colored inks, e.g., magenta, cyan
and yellow. The colors from the three color pens are mixed to
obtain any particular color.
The pens are typically mounted in stalls within an assembly which
is mounted on the carriage of the printer/plotter. The carriage
assembly positions the inkjet pens and typically holds the
circuitry required for interface to the heater circuits in the
inkjet pens.
Full color printing and plotting requires that the colors from the
individual pens be precisely applies to the media. This requires
precise alignment of the carriage assembly. Unfortunately,
mechanical misalignment of the pens in conventional inkjet
printer/plotters results in offsets in the X direction (in the
media or paper axis) and in the Y direction (in the scan or
carriage axis). This misalignment of the carriage assembly
manifests as a misregistration of the print images applied by the
individual pens. In addition, other misalignments may arise due to
the speed of the carriage, the curvature of the platen and/or spray
from the nozzles.
However, the integration of the optical and electronic components
in the optical sensor, as well as positioning the optical sensor on
the carriage have been complicated, expensive and to some extent
imprecise in prior printers/plotters. The need for reliability and
precision is even greater in recent inkjet printers/plotters which
print high resolution color graphics and images, often on very
large poster-size printouts.
Also, it is desirable to simplify the circuitry on the optical
sensor in order to facilitate easy inexpensive production and
assembly without the need for an excessive number of parts.
BRIEF SUMMARY OF THE INVENTION
Accordingly, it is a general object of the invention to provide a
modular structure which integrates the optical and electronic
components in a simplified but reliable way on an optical sensor
unit.
More specifically, the invention contemplates a carriage-mounted
optical sensor for an inkjet printer/plotter which includes a
modular flex-circuit assembly which has a co-planar junction on a
first end and a circuit-board interconnect on the other end. The
co-planar junction directly interconnects electrically with all of
the electronic components on the optical sensor unit and also
provides structural support through wire leads from a photocell and
LEDs. Additional optical and positioning components are then
self-attachable to the modular flex-circuit assembly to form an
optical sensor unit having the LEDs positioned to transmit light to
a print zone, and having the photocell positioned to receive
reflected light from the print zone. A protective casing surrounds
and supports the electronic and optical components in the sensor
unit and also is self-attachable and pre-positioned through X/Y/Z
axis datums to the carriage. Separate activation circuits are
provided for each LED to allow different LEDs such as LEDs emitting
different colored light to be selectively activated depending on
the type of markings on the media.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a large format inkjet
printer/plotter incorporating the features of the present
invention;
FIG. 2 is close-up view of the carriage portion of the
printer/plotter of FIG. 1 showing a carriage-mounted optical sensor
of the present invention;
FIG. 3 is a close-up view of the platen portion of the
printer/plotter of FIG. 1 showing the carriage portion in phantom
lines;
FIG. 4 is a schematic representation of a top view of the carriage
showing offsets between individual printheads in the media advance
axis and in the carriage scan axis;
FIG. 5A is an isometric view showing a fully assembled optical
sensor unit incorporating a presently preferred embodiment of the
invention;
FIG. 5B is a bottom view of the optical sensor unit taken along the
line 5B--5B in FIG. 5A;
FIG. 6 is a front view of the optical components of the sensor unit
of FIG. 5A;
FIGS. 7A, 7B, 7C, 7D and 7E are a sequential representation showing
a presently preferred set of modular assembly steps for the optical
sensor unit;
FIG. 8 is an isometric view looking down from the right front side
of the carriage showing the optical sensor and one print cartridge
mounted on the carriage;
FIG. 9 is an isometric view looking up from the right rear side of
the carriage showing the optical sensor and one print cartridge
mounted on the carriage;
FIG. 10 is an isometric view looking down from the right rear side
of the carriage showing the optical sensor mounted on the
carriage;
FIG. 11 is a top view of the entire flex-circuit showing the
details of the co-planar junction portion at a first end of the
flex-circuit;
FIG. 12 is a top view identifying an exemplary circuit arrangement
at a second end of the flex circuit;
FIG. 13 is an enlarged sectional view showing an exemplary
through-hole for the co-planar junction portion; and
FIG. 14 is a schematic representation showing the interconnection
between the circuitry interconnections between the flex-circuit and
the photocell.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
FIG. 1 is a perspective view of an inkjet large format
printer/plotter incorporating the teachings of the present
invention. The printer 210 includes a housing 212 mounted on a
stand 214. The housing has left and right drive mechanism
enclosures 216 and 218. A control panel 220 is mounted on the right
enclosure 218. A carriage assembly 300, illustrated in phantom
under a cover 222, is adapted for reciprocal motion along a
carriage bar 224, also shown in phantom. The position of the
carriage assembly 300 in a horizontal or carriage scan axis is
determined by a carriage positioning mechanism 310 with respect to
an encoder strip 320 (see FIG. 2). A print medium 330 such as paper
is positioned along a vertical or media axis by a media axis drive
mechanism (not shown). As used herein, the media axis is called the
X axis denoted as 201, and the scan axis is called the Y axis
denoted as 301.
FIG. 2 is a perspective view of the carriage assembly 300, the
carriage positioning mechanism 310 and the encoder strip 320. The
carriage positioning mechanism 310 includes a carriage position
motor 312 which has a shaft 314 which drives a belt 324 which is
secured by idler 326 and which is attached to the carriage 300.
The position of the carriage assembly in the scan axis is
determined precisely by the encoder strip 320. The encoder strip
320 is secured by a first stanchion 328 on one end and a second
stanchion 329 on the other end. An optical reader (not shown) is
disposed on the carriage assembly and provides carriage position
signals which are utilized by the invention to achieve optimal
image registration in the manner described below.
FIG. 3 is perspective view of a simplified representation of a
media positioning system 350 which can be utilized in the inventive
printer. The media positioning system 350 includes a motor 352
which is normal to and drives a media roller 354. The position of
the media roller 354 is determined by a media position encoder 356
on the motor. An optical reader 360 senses the position of the
encoder 356 and provides a plurality of output pulses which
indirectly determines the position of the roller 354 and,
therefore, the position of the media 230 in the X axis.
The media and carriage position information is provided to a
processor on a circuit board 370 disposed on the carriage assembly
100 for use in connection with printhead alignment techniques of
the present invention.
The printer 210 has four inkjet print cartridges 302, 304, 306, and
308 that store ink of different colors, e.g., black, magenta, cyan
and yellow ink, respectively. As the carriage assembly 300
translates relative to the medium 230 along the X and Y axes,
selected nozzles in the inkjet print cartridges 302, 304, 306, and
308 are activated and ink is applies to the medium 230. The colors
from the three color cartridges are mixed to obtain any other
particular color. Sample lines 240 are typically printed on the
media 230 prior to doing an actual printout in order to allow the
optical sensor 400 to pass over and scan across the lines as part
of the initial calibration.
The carriage assembly 300 positions the inkjet print cartridges and
holds the circuitry required for interface to the ink firing
circuits in the print cartridges. The carriage assembly 300
includes a carriage 301 adapted for reciprocal motion on front and
rear slider rods 303, 305.
As mentioned above, full color printing and plotting requires that
the colors from the individual print cartridges precisely applied
to the media. This requires precise alignment of the carriage
assembly as well as precise alignment of the print cartridges in
the carriage. Unfortunately, paper slippage, paper skew, and
mechanical misalignment of the print cartridges results in offsets
in the X direction (in the media advance axis) and in the Y
direction (in the carriage or axis) as well as angular theta
offsets. This misalignment causes misregistration of the print
images/graphics formed by the individual ink drops on the media.
This is generally unacceptable as multi-color printing requires
image registration accuracy from each of the printheads to within
1/1000 inch (1 mil).
FIG. 4 shows a presently preferred embodiment of printheads each
having two groups of nozzles with a column offset 410. By comparing
the relative positions of corresponding nozzles in different
printheads along the Y axis, it is possible to determinine an
actual horizontal offset 412 between two printheads, and by
comparison with a nominal default offset 414 determine an actual
offset 416 in the carriage scan axis. This is repeated for all of
the different printheads while they remain on the carriage.
Similarly, by comparing the relative positions of corresponding
nozzles in different printheads along the X axis, it is possible to
determine an actual vertical offset 418 in the media advance axis.
This is also repeated for all of the different printheads while
they remain on the carriage.
In order to accurately scan across a test pattern line, the optical
sensor 400 is designed for precise positioning of all of its
optical components. Referring to FIGS. 5A, 5B, and 6, the sensor
unit includes a photocell 420, holder 422, cover 424, lens 426, and
light source such as two LEDs 428, 430. A unitary light tube or cap
432 has a pair of notched slots 434 which engage matching tabs 436
on a lower end of the holder 422 upon insertion and relative
rotation between the cap and the holder. The two LEDs are held in
opposite apertures of two shoulders 438 which have a size slightly
less than the outside diameter of the LEDs, to prevent the LEDs
from protruding into a central passageway which passes through the
holder to the photocell.
A protective casing 440 which also acts as an ESD shield for the
sensor components is provided for attachment to the carriage as
well as for direct engagement with the shoulders of the light tube.
In that regard, the top of the shoulders are sized and shaped to
snugly fit inside downwardly tapered side walls 442 of the casing,
with the top of the LEDs abutting against an upstanding flange 444
and with a lower portion of the shoulders held tightly by arms 446
which flex outwardly to an open position while the light tube is
being pushed into a position of engagement with the casing. Upon
completion of the engagement, the arms return to a closed latched
position with a lip 448 on the end of each arm 446 preventing
disengagement of the light tube (and its LEDs) during normal
use.
FIGS. 7A-7E show a preferred sequence of steps for assembling the
optical sensor. Firstly, a modular flex-circuit assembly is created
with an elongated TAB circuit 450 having a junction portion 452
with soldered through-holes which (a) connect and support a first
pair of wire leads 454 to one LED, (b) connect and support a second
pair of wire leads 456 to another LED, and (c) connect and support
a set of three wire leads 458 coming from the photocell (FIG. 7A).
Secondly a U-shaped cover 424 holds the photocell in nested
position at the upper end of the holder, while the LEDs and holder
are positioned by the light tube (FIGS. 7B-7C). Finally, the
subassembly is inserted into the casing, with a free end 462 of the
TAB circuit extending out through an access slot in the casing
(FIGS. 7D and 7E).
It will be appreciated by those skilled in the art from the
foregoing description that the invention provides a self-fixturing
modular assembly whereby the light tube acts as a cap for holding
both the two LEDs as well as the lens/holder/photocell/cover
composite in fixed relative positions. Accordingly, if desirable
the soldering of the interconnections at the co-planar junction
portion of the flex-circuit can be done after assembly of the
various component parts held by the cap.
The fully assembled optical sensor unit can then be placed inside
of vertical rib 464 and against back plate 466 for self-attachment
by rear tab 468, front notch 470, and lower front hook 472 to
matching X/Y/Z datum-like surfaces on the carriage (see FIGS.
8-10).
It will be understood by those skilled in the art that by having
the electronic components of the optical sensor all connected
through a common co-planar junction portion of a flex-circuit
allows the flex-circuit to be small and less costly. Also, it
allows for the substitution of an even less expensive printed
circuit board at the common junction if necessary.
The specification details of the flex-circuit member and its
co-planar junction are shown in FIGS. 11-13, and are self
explanatory. It is noted that the co-planar junction 452 is wider
than the rest of the TAB circuit to allow sufficient space for a
pair of solder connections 480 for a blue light LED, a pair of
solder connections 482 for a green light LED, and a set of three
solder connections 484 for the photocell. A first activation line
486 connects the blue light LED and a second separate activation
line 488 connects the green light LED to allow independent control
over the LEDs depending on the media markings. It is noted that in
this particular embodiment, the green light LED is used to sense
media markings made by black, or cyan, or magenta ink, while the
blue light LED is used to sense media markings made by yellow
ink.
The details of the through-holes in the junction portion are shown
in FIG. 13, with an enlarged diameter upper hole 490 through a
polyimide coverlay 492 and an smaller diameter lower hole 493
through a polyimide base 494 and a copper conductor layer 495.
Acrylic adhesive layers 496 provide the required lamination for the
TAB circuit. A small bottom stiffener layer 498 provides support
for exposed ends of the conductors to be connected to a carriage
circuit board such as through a zif connector.
The circuitry for both the photocell 420 (with amplifier) as well
as for the green light and blue light LEDs is shown schematically
in FIG. 14.
The benefits and details of the optical features of the unitary
light tube are more fully described in the previously identified
co-pending application entitled OPTICAL PATH OPTIMIZATION FOR LIGHT
TRANSMISSION AND REFLECTIONIN A CARRIAGE-MOUNTED INKJET PRINTER
SENSOR.
It should be understood that various changes and modifications can
be made to the illustrated embodiments of the invention described
herein, all without departing from the spirit and scope of the
invention as set forth in the following claims.
* * * * *